The proposed Program which consists of six Projects and three Core resources will continue to involve the sustained efforts of several members of the University of Chicago in an attempt to eucidate the structure and function of two main classes of serum lipoproteins, low-density (LDL) and high density (HDL), through a variety of physical, chemical and enzymatic techniques and to utilize this information in the analysis of the mechanisms regulating lipoprotein-lipoprotein and lipoprotein-cell interactions. The studies will be carried out in human subjects and dogs, will make use of two types of cells, cultured skin fibroblasts and granulocytes isolated from blood, and will also utilize model lipid vesicles. Once the normal parameters are established the work will be extended to the study of modfied cell and lipoprotein surface and eventually to dyslipoproteinemic states in man. The work which has a common theme and an integration in efforts is expected to provide an understanding of lipid-protein interactions in general and of the molecular events attending the interaction between lipoproteins and cells; they are also expected to give a better insight into the mechanisms whereby serum lipoproteins may regulate cell function.